[OpenAFS] Re: Possible cache corruption with linux client and 1.6.1 fileserver

Richard Brittain Richard.Brittain@dartmouth.edu
Wed, 14 Nov 2012 14:04:38 -0500 (EST)

On Tue, 13 Nov 2012, Andrew Deason wrote:

> On Tue, 13 Nov 2012 13:58:11 -0500
> Jeffrey Altman <jaltman@your-file-system.com> wrote:
>> If it is always 4KB at the beginning of the file I do not think
>> Andrew's patch is going to be the solution.   It is certainly worth
>> trying if you can but in this scenario to get a 4KB at the beginning the
>> client would need to have issued an RXAFS_FetchData() for offset 0 and
>> length 0 and have received back 0 bytes and status info indicating that
>> the new length of the file is 4KB.
>> I believe that Andrew's patch addresses the case where a chunksize is
>> say 64KB and the client issues a read for 1KB and the file server says
>> the file is really 4KB in length.  The client would show 1KB of data
>> followed by a 3KB hole.
>> Andrew, please correct me if I'm wrong.

Someone just told me how to clear linux buffer cache using 
/proc/sys/vm/drop_caches, and doing that will 'fix' the file too - no need 
to re-read the file from the fileserver.  It looks like the problem is 
between the cache manager and the Linux buffer cache.  That is consistent 
with the V-files in the cache apparently containing the correct data.


Richard Brittain,  Research Computing Group,
                    Computing Services, 37 Dewey Field Road, HB6219
                    Dartmouth College, Hanover NH 03755
Richard.Brittain@dartmouth.edu 6-2085